This was the core of the issue I was raising in the last thread about
this (the one following the rename to suspend blockers). Essentially
what happens in a mainline context is that some subsystems can with
varying degress of optionality ignore some or all of the instruction to
suspend and keep bits of the system alive during suspend.
Those that stay alive will either have per subsystem handling or will be
outside the direct control of the kernel entirely (the modem is a good
example of the latter case in many systems - in terms of the software
it's essentially a parallel computer that's sitting in the system rather
than a perhiperal of the AP).